1. Field of the Invention
The present invention relates to a motor drive apparatus using a Hall element.
2. Description of the Related Art
As a method of driving a single-phase motor, a method is known in which rotor position is detected using a Hall element, and coil current is controlled by applying voltage to a coil of the single-phase motor in accordance with rotor position information, to control rotation of the rotor (Patent Document 1).
Conventionally, as described in FIG. 1 of Patent Document 1, an output signal of the Hall element is inputted to a hysteresis comparator and converted to a rectangular wave signal, and the coil of the motor is energized to perform rotation control, by turning ON and OFF transistors forming a H-bridge circuit based on the rectangular wave signal. At this time, at timing in which phase is shifted, by delaying the rectangular wave signal outputted from the hysteresis comparator, a time-period (referred to below as dead time) is arranged, in which, among the transistors forming the H-bridge circuit, two transistors connected in series between a power supply and ground are both OFF. As a result, when the phase is switched, flow of breakthrough current in transistors forming the H-bridge circuit is inhibited.
Patent Document 1: Japanese Patent Application, Laid Open No. H7-87775
In cases in which a motor is driven with a dead time interval, as in technology described in Patent Document 1, during a dead time period, regenerative current flows via a freewheel diode arranged in parallel to a transistor forming the H-bridge circuit.
However, with the technology described in Patent Document 1, there have been cases in which time waveform of the regenerative current flowing via the freewheel diode changes rapidly, or has a large peak. As a result, there has been a risk of a large noise being generated, or of a large voltage being applied to a transistor that forms an output circuit such as the H-bridge circuit or the like, by a reverse voltage.